1. Technical Field
The present disclosure relates to an image processing method and an image processing apparatus for forming an image on a recording medium by discharging an ink droplet.
2. Description of the Related Art
An ink-jet recording apparatus records an image on a recording medium by discharging ink droplets from nozzles disposed on a recording head. It is known that when the ink-jet recording apparatus has been in a long waiting time without recording an image on a recording medium, water in ink in a nozzle is evaporated, and as a result, the ink is condensed. In particular, evaporation of water in ink tends to easily occur close to a discharge orifice of a nozzle and thus density tends to become high close to the discharge orifice. If an ink droplet is discharged from a nozzle in a state in which the ink is condensed close to its discharge orifice, the discharged ink droplet has a higher density than usual. After the ink droplet is discharged, non-condensed ink is supplied from an ink tank, and thus condensation of ink in the nozzle disappears. Thus, after a nozzle has been in a standby state for a long time without being used in recording an image, if an image is recorded using this nozzle, the intensity becomes high at an edge of the image.
To suppress unevenness in density of an image caused by condensation of ink, Japanese Patent Laid-Open No. 2002-326347 discloses a technique of correcting the unevenness in density by reducing a density signal such that the amount of reduction increases with time period in which no ink is discharged.
However, in a case where the density signal is corrected using the technique disclosed in Japanese Patent Laid-Open No. 2002-326347, there is a possibility that degradation in image quality occurs, which makes it difficult to obtain a high-quality image depending on the type of the image. FIG. 1A illustrates an edge part of a character in a state before a correction is performed, and FIG. 1B illustrates the edge part of the character after the correction is performed. In the case where the correction process is performed on an image including a character using the technique disclosed in Japanese Patent Laid-Open No. 2002-326347, part of dots at an edge of the character are lost via the correction process, which causes unevenness to occur at the edge and thus the edge becomes blurred. This causes degradation in quality of characters in an image. The above situation occurs not only in an image including a character but may also occur in an image including a thin line or the like.
In view of the above, the present invention provides an image processing method capable of performing a correction process properly based on a degree of condensation of ink in a nozzle so as to suppress unevenness in density in an image while minimizing degradation in image quality of a character, a thin line, or the like.